What’s the difference between a ninja and a trottoir roulant? One we know; the other is a complicated moving walkway system first introduced in Paris in 1900. Don’t get mixed up, though – the trottoir roulant isn’t your typical airport walkway, designed to move groups of sluggish Americans (usually) from one domestic gate to the next. The trottoir roulant is, however and in fact, the ninja of moving walkways: avant garde, complex, multi-faceted, able to operate at multiple speeds and sometimes, even, in multiple directions.

The trottoir never quite picked up as much speed as it could have, though plans for walkways across the Brooklyn Bridge in New York were vaguely thrown around at the beginning of the century, while thirty years even before that, a local wine seller named Alfred Speer (no relation?) tried to convince the good people of Manhattan that what they really needed was a moving sidewalk. HG Wells got ahold of the idea and wrote about it in a short story; the engineers of London’s Underground built the Travelator; and in 2003, a Troittoir Roulant Rapide was unveiled in Paris’ Montparnasse Metro station (only to be taken out of service in May of last year.)

What can we learn from this? First, that laziness knows no bounds. Second, that not all super-stellar ideas can be built. And third, that when it comes to moving walkways, it might be better to think out of the box about where these trottoirs might actually come in handy. Herewith, then, we offer you the Ultimate Moving Walkway Guide, Ninja-Style

1. The Guggenheim New York

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The Pitch: Much has been made of the exhibition design in this Upper East Side Manhatan museum. You walk in, see a big atrium, and then a ramp, going up. The obvious choice is to walk up to the friendly ticket-taker, give up your paid-for (ninjas are ruthlessly honest, after all) ticket, and head on up the show. Problem is, architect Frank Lloyd Wright actually intended for people to take the elevator up to the top and walk down. Some exhibitions at the Guggenheim have only worked if visitors start at the top and head down; others have been designed to operate chronologically, starting form the bottom. Most of the time, people end up just confusedly wandering on through the space, starting at the top, the bottom, the middle. A perfectly installed trottoir roulant would render all these problems irrelevant, while still, being reversible in direction, allowing for at least two exhibition takes.

Upsides: Easy to install; the space is practically begging for it; Frank Lloyd Wright would probably roll over in his grave.

Downsides: Art should sometimes be looked at with a leisurely pace; the museum would lose its sense of easy ambling; Frank Lloyd Wright would probably roll over in his grave.

2. Sagrada Familia

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The Pitch: This Barcelona church, designed by Antonio Gaudi, has been under construction for the last million years and will continue to be for the next thousand. (Note: numbers not accurate). Thing is, visitors are undeterred by its incompleteness and just want to come gawk at the millions (numbers accurate) of mosaic parts. And the problem is, the most thrilling parts of the building are up at the top. Solution? A moving walkway that weaves in and out of the eighteen bell towers, so that people can get right up close to all that detail work. It’s one thing to see the four pillars of the Nativity Façade from down on the ground; it’s quite another to get right up in there, ninja-style.

Upsides: Easier access to great art; the design’s just crazy enough for some airborne walkways to slip right in; it would be a “familia” process.

Downsides: The church might become more Blade Runner, less Barcelona; the symbology would get thrown out of wack; What Would Gaudi Do?

3. Villa Savoye

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The Pitch: As Le Corbusier wrote of the ramp in the Villa Savoye, it produces “ a gradual ascent from the pilotis, creating totally different sensations than those felt when climbing stairs. A staircase separates one floor from another; a ramp links them together.” What Corb forgot is that the process of walking up a ramp is not so unlike the process of walking upstairs; footfalls separate from each other, creating a series of isolated movements instead of one smooth ninja ascent. The perfect fix? Install a trottoir roulant in this Poissy House, and glide straight from French soil to the calisthenics-appropriate roof.

The Upside: It all started in France anyway; this would be a physical iteration of Corb’s super-futuristic mentality; increased space for jumping jacks.

The Downside: This is the Villa Ninja-Freakin Savoye! Not meant for such frivolities.

4. CityCenter Las Vegas

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The Pitch: This latest mega (possibly megalo-) – billion-dollar project to hit the Las Vegas strip opened just a few short weeks ago to a level of fanfare that made it feel like we were all back in the heady weekly-groundbreaking days of 2006. What better idea, then, to travel all the way back in time to turn-of-the-century Paris and install a moving walkway around this multi-building complex? It could start at Jenny Holzer’s spectacular installation, Vegas, in the underground parking garage of the Aria, move up the ramp to pass by Rafael Vinoly’s Vdara, and curve back around past Nancy Rubins’ canoe sculpture, Big Edge. For extra credit, the walkway could jump into Daniel Libeskind’s Jewish Museum-reminiscent Crystals shopping center and climb up the side of David Rockwell’s treehouse. After all, what good are architectural angles if you can’t stick yourself to a moving walkway/wall and play Don’t Touch The Floor?

The Upside: Vegas is a city of such wack-tastic scale that even the sharpest-eyed ninja can get temporally confused: a walkway would help diminish that sense of Sisyphean no-progress.

The Downside: With all the Sirio Maccioni food and free-if-you’re-gaming cocktails, Vegas visitors probably need all the exercise they can get.

5. Salk Institute

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The Pitch: This Louis Kahn building was rendered particularly infamous in his son Nathaniel’s movie, My Architect, in which the relatively estranged offspring roller-skated all over the concrete plaza. Imagine, then, if Nathaniel could have done the same curving swoops, the same leg extensions, the same balletic moves, without having to worry about catching his skates on an errant paternal crack. Imagine, in other words, a series of moving walkways, wending every which way, allowing riders to perform leaps, arabesques, and demi detournes.

The Upside: Architecture with this much space is practically crying out for some version of parkour; Kahn might have appreciated it; the Salk Institute scientists could probably use a little fun.

The Downside: Walkways would remove that sense of absolute mobility and freedom; the younger Kahn would have to deal with his father issues alone in a crowd; the Salk Institute scientists probably don’t need any more distraction.

While it might seem implausible that any of these additions will ever see the light of construction, the point is not to focus on what the trottoir roulant can do for you. Focus, instead, on what you can do for the trottoir roulant, and on seeing these buildings through the lens of play, engagement, and general ninja-tastic awesomeness. Architecture has never been static; the idea of a moving walkway is just another reminder.

The below video, filmed at the Exposition in 1900 is playful display of human curiosity.